Retaining Walls: East Honolulu vs Mililani Town
How do retaining walls rules compare between East Honolulu, HI and Mililani Town, HI?
East Honolulu and Mililani Town have similar restriction levels.
East Honolulu, HI
Honolulu County
East Honolulu retaining walls on Kuliouou, Hawaii Loa Ridge, and Niu Valley hillsides fall under ROH 21-4.40, which caps fill-bearing walls in required yards at 6 feet with terraced heights combined.
View full East Honolulu rules →Mililani Town, HI
Honolulu County
Mililani Town retaining walls follow ROH Sec. 21-4.40 rules and HOA review. Fill-retaining walls in required yards cannot exceed 6 feet, and terraced walls are measured in combination.
View full Mililani Town rules →Key Facts Comparison
| Fact | East Honolulu | Mililani Town |
|---|---|---|
| Yard max height | 6 feet | - |
| Terraced rule | Heights combined | - |
| Code section | ROH 21-4.40 | - |
| Engineering trigger | Above 30 inches | - |
| - | - |
Highlighted rows indicate differences between cities.
East Honolulu FAQ
How tall can a Hawaii Kai retaining wall be?
Walls containing fill in a required yard cap at 6 feet under ROH 21-4.40. Terraced walls are measured as combined height. Engineering review is required above the 30-inch permit threshold for hillside lots.
Do Kuliouou hillside walls need extra review?
Yes. Steep Kuliouou and Hawaii Loa Ridge sites typically require geotechnical and drainage review, engineered drawings, and sometimes grading permits under Chapter 14 alongside the 21-4.40 retaining wall rules.
Mililani Town FAQ
Do planter walls count as retaining walls?
If they hold back soil, yes; decorative low planters that don't retain earth are typically not regulated under 21-4.40.
Is HOA approval needed for a 24-inch garden wall?
Usually yes. Even ROH-exempt walls typically still need HOA architectural review in Mililani before construction.
Compare other topics
See how East Honolulu and Mililani Town compare on other ordinance categories.
Want to add a third city?
Use our full comparison tool to compare up to three cities.
Open Comparison Tool